Issues with Restful Jersey and JSON - rest

Question

I have a strange issue and didn't find any information about it at all.
Having a simple POJO like (simplified..)
#XmlRootElement
public class Bill {
List<Position> positions
.. getter/setter
}
#XmlRootElement
public class Position {
.. some simple properties with getters/setters
}
I am unable to call a RESTful Service using instances of these classes. I'm getting real weird errors I don't really understand.
org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of java.util.List out of START_OBJECT token
The funny thing is, when I just test serialization/deserialization using Jackson Object mapper directly, it works as expected!
ObjectMapper mapper = new ...
mapper.writeValue(stringWriter, bill);
mapper.readValue(stringWriter.toString(), Bill.class);
This works perfectly. So I guess the POJO itself is OK and Jackson is able to handle the JSON-String.
Calling the RESTful service using the same Bill instance fails with the error mentioned above. I see it is using Jackson as well, here is part of stack trace:
at org.codehaus.jackson.map.JsonMappingException.from(JsonMappingException.java:160)
at org.codehaus.jackson.map.deser.StdDeserializationContext.mappingException(StdDeserializationContext.java:198)
at org.codehaus.jackson.map.deser.CollectionDeserializer.deserialize(CollectionDeserializer.java:103)
at org.codehaus.jackson.map.deser.CollectionDeserializer.deserialize(CollectionDeserializer.java:93)
at org.codehaus.jackson.map.deser.CollectionDeserializer.deserialize(CollectionDeserializer.java:25)
at org.codehaus.jackson.map.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:230)
And here is how the RESTful Application is configured:
#javax.ws.rs.ApplicationPath("rest")
public class ApplicationConfig extends Application {
public Set<Class<?>> getClasses() {
return getRestResourceClasses();
}
/**
* Do not modify this method. It is automatically generated by NetBeans REST support.
*/
private Set<Class<?>> getRestResourceClasses() {
Set<Class<?>> resources = new java.util.HashSet<Class<?>>();
resources.add(rest.RestAPI.class);
// following code can be used to customize Jersey 1.x JSON provider:
try {
Class jacksonProvider = Class.forName("org.codehaus.jackson.jaxrs.JacksonJsonProvider");
resources.add(jacksonProvider);
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(getClass().getName()).log(java.util.logging.Level.SEVERE, null, ex);
}
return resources;
}
}
Do you have any idea what I'm missing?
I generated the service and the client with NetBeans. Oh and it works when I use XML instead of JSON.
Any help would be very much appreciated.

Answer 1

I'm sorry but after hours of testing and debugging I finally found the cause of the problem.
Still I would be very interested why this is?
Commenting out the following code did the trick:
// following code can be used to customize Jersey 1.x JSON provider:
try {
Class jacksonProvider = Class.forName("org.codehaus.jackson.jaxrs.JacksonJsonProvider");
resources.add(jacksonProvider);
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(getClass().getName()).log(java.util.logging.Level.SEVERE, null, ex);
}